Recently, the demand for portable electronic products such as notebook computers, video cameras and portable telephones has increased sharply, and electric vehicles, energy storage batteries, robots, satellites and the like have been developed in earnest. Accordingly, high-performance secondary batteries allowing repeated charging and discharging are being actively studied.
Secondary batteries currently commercialized include nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, lithium secondary batteries and so on. Among them, the lithium secondary batteries are more highlighted in comparison to nickel-based secondary batteries due to advantages such as free charging and discharging, caused by substantially no memory effect, very low self-discharge rate, and high energy density.
The lithium secondary battery mainly uses lithium-based oxides and carbonaceous materials as a positive electrode active material and a negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate coated with the positive electrode active material and a negative electrode plate coated with the negative electrode active material are disposed with a separator being interposed therebetween, and an exterior, namely a battery case, for sealably containing the electrode assembly together with an electrolyte.
Generally, the lithium secondary battery may be classified into a can-type secondary battery in which the electrode assembly is included in a metal can and a pouch-type secondary battery in which the electrode assembly is included in a pouch made of aluminum laminate sheets, depending on the shape of the exterior.
In the can-type secondary battery, a metal can in which an electrode assembly is included may be fabricated in a cylindrical form. The can-type secondary battery may be used to construct a battery module with a housing that accommodates a plurality of secondary batteries.
However, if the plurality of secondary batteries are accommodated in the inner space of the housing of the battery module without a securing means, in an environment where shocks caused by shaking or rattling are frequently applied to a running vehicle to which the battery module is mounted, the secondary battery is frequently moved inside the accommodation space of the housing, which may cause damage to the secondary battery or disconnection between the electrode terminal and the bus bar.
Thus, in recent years, various methods have been attempted to fix the plurality of secondary batteries accommodated in the housing without movement inside the accommodation space. For example, an attempt is made to apply a method of securing the secondary batteries inside the housing with an adhesive.
However, the adhesive applied to the housing is easy to flow down from the inner surface of the accommodation space of the housing. Thus, the adhesive may be lost out of the housing, and it is difficult to maintain the uniform distribution and constant thickness of the adhesive on the inner surface of the housing.
Moreover, the adhesive lost out of the housing may contaminate other components of the battery module to cause product defects or contaminate the work environment to disturb operations of workers. Further, since the adhesive is not uniformly distributed and cured on the inner surface of the accommodation space of the housing, the secondary battery fixed in the accommodation space of the housing may be easily released, which makes it difficult to prevent the secondary battery from being damaged or the connection between the electrode terminal and the bus bar from being cut.
Thus, it is necessary to develop a technology for an improved method for manufacturing a battery module to solve the above problem.